1. Technical Field
This disclosure relates to an apparatus and method for forming images, and more specifically, to an apparatus and method for forming images by ejecting liquid containing color materials.
2. Description of the Background Art
Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatuses are known inkjet-type image forming apparatuses (hereinafter, inkjet recording apparatus) having one or more recording heads for ejecting droplets of ink or other liquid.
With increasing demands for easily recording color images, such inkjet recording apparatuses have been widely used to form (record) color images on media for recording, such as sheets of paper (hereinafter, recording media) by ejecting ink droplets of different colors from the recording heads. A conventional type of inkjet recording apparatuses stop image recording when one of the different color inks runs out. However, there are demands from users for forming images using the other color inks even when one color is out of ink.
Hence, a conventional technique is proposed to output black-and-white images in only black ink when color inks (i.e., inks having colors other than black) run out and full-color output becomes unexecutable. In such a technique, the remaining amounts of basic constituent inks are detected to select one of full-color output and black-and-white output, thus allowing the black-and-white output to be executed even when color inks run out. Generally, after ejecting ink droplets from ejection ports of the recording heads, inkjet recording apparatuses may suction a predetermined amount of ink from the ejection ports to recover the ejection performance of the heads. However, a conventional inkjet recording apparatus simultaneously suctions the ejection ports for the respective color inks during recovery operation. Accordingly, for the above-described technique, ink is suctioned from nozzles from which ink droplets have not been ejected, thus wasting ink.
Hence, another technique is proposed for an inkjet recording apparatus that have a plurality of recording heads and a suction recovery unit and performs a sequence of operation in which suction recovery is performed on only a selected head(s). For this technique, when recording is performed using only a particular head(s) of the plurality of recording heads, the suction recovery is not performed on the other heads not used for the recording, thus preventing waste of ink.
Meanwhile, when the ejection ports of nozzles not used for recording are opened to ambient air, an increase in the viscosity of ink extends deep into the nozzles over time. In such a case, even if the suction recovery is performed on such nozzles to use the nozzles in the next recording, the increased viscosity of ink may not be completely removed. As a result, an ejection failure may occur, thus hampering accurate image formation.